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71.
-erythro- and
-threo-β-methylphenylalanines were synthesized and incorporated into the delta opioid receptor-selective deltorphin C peptide by solid-phase peptide synthesis. The enantiomeric composition of β-methylphenylalanine and the diastereomeric composition of the peptide were determined. To distinguish exactly between the two enantiomeric pairs of β-methylphenylalanine, different liquid, gas and thin-layer chromatographic methods are suggested, while the four diastereomers Of [β-Mephe3]deltorphin C Can be identified and separated conveniently by high-performance liquid chromatography. 相似文献
72.
The results of dielectric studies performed in a broad frequency range for two compounds, 4-cyanophenyl 4-n-heptylbenzoate (7BBCN) and 4-(4-cyanobutyloxy)phenyl 4- n-heptylbenzoate (7BB4CN), are compared. They have the same molecular core whereas the strongly polar CN group is attached to the benzene ring in 7BBCN or is separated from it by the butyloxy chain in 7BB4CN. 7BBCN has a nematic phase, whereas 7BB4CN exhibits a monotropic nematic and smectic A2 polymorphism. Large differences in the dielectric properties of the two substances were found. The analysis of the results led to the conclusion that the antiparallel dipole-dipole associations are considerably stronger in the substance with a decoupled CN group. 相似文献
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Dirk Mehlhorn Dr. Rustem Valiullin Prof. Dr. Jörg Kärger Kanghee Cho Prof. Dr. Ryong Ryoo 《Chemphyschem》2012,13(6):1495-1499
Specially synthesized extra‐large crystallites of zeolite LTA with intentionally added mesoporosity are used for an in‐depth study of guest diffusion in hierarchical nanoporous materials by the pulsed field gradient NMR technique. Using propane as a guest molecule, intracrystalline mass transfer is demonstrated to be adequately described by a single effective diffusivity resulting from the weighted average of the diffusivities in the two (micro‐ and meso‐) pore spaces. Gas‐kinetic order‐of‐magnitude estimates of the diffusivities are in satisfactory agreement with the experimental data and are thus shown to provide a straightforward means for predicting and quantifying the benefit of hierarchically structured nanoporous materials in comparison with their purely microporous equivalent. 相似文献
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Ann Kathrin Stark Michael Schilling Dirk Janasek Joachim Franzke 《Analytical and bioanalytical chemistry》2010,397(5):1767-1772
A novel electrospray interface is presented which induces an electric field by dielectric polarization through a non-conductive barrier. Therefore, a square-wave high-voltage signal is applied. This technique allows mass spectrometric measurements in the positive as well as in the negative mass spectrometry mode without changing the polarity of the potential applied, and it decreases the risk of undesired discharges, induced by high electric currents. The applicability of this technique is demonstrated by mass spectrometric determination of reserpine. 相似文献